[PROJ] Fwd: some help with cm-level GRS80 to WGS-84 transformation?

[Lesparre, Jochem]

Dear Joe,

For this case in cs2cs you have to add a +towgs84 parameter too. If you don’t want a datum transformation: +towgs84=0,0,0,0,0,0,0 on both sides.

Regards, Jochem





From: PROJ <proj-bounces at lists.osgeo.org> On Behalf Of Joseph Boardman
Sent: woensdag 19 januari 2022 21:25
To: proj at lists.osgeo.org
Subject: [PROJ] Fwd: some help with cm-level GRS80 to WGS-84 transformation?





-------- Forwarded Message --------
Subject:
some help with cm-level GRS80 to WGS-84 transformation?
Date:
Wed, 19 Jan 2022 11:28:24 -0700
From:
Joseph Boardman <boardman at aigllc.com><mailto:boardman at aigllc.com>
To:
proj at lists.osgeo.org<mailto:proj at lists.osgeo.org>


Dear Proj Experts,

I'm a remote sensing geophysicist with experience in geodesy and mapping.

Right now I'm struggling trying to get a high-accuracy proj command to convert from GRS80 to WGS-84 at the cm level.

Any clues? cs2cs is not doing it.

cs2cs +proj=lonlat +ellps=WGS84 +to +proj=lonlat +ellps=GRS80 -d 8
-120 40
-120.00000000   40.00000000 0.00000000

Do I need to do a transformation pipeline per the 8.2.1 docs and use a Helmert transform? Any help much appreciated.

Best,

Joe




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